What effect does aldosterone have on potassium levels?

• A. Aldosterone enhances potassium absorption
• B. Aldosterone promotes renal excretion of potassium
• C. Aldosterone has no effect on potassium levels
• D. Aldosterone decreases renal blood flow

Answer: (B)

Aldosterone is a hormone produced by the adrenal glands, and its primary role is to regulate sodium and potassium levels within the body. Specifically, aldosterone acts on the cells of the kidney, particularly in the distal convoluted tubule and the collecting duct. It promotes sodium reabsorption, which indirectly affects potassium levels.

When aldosterone is secreted, it enhances the activity of sodium channels in the tubular cells, allowing for increased sodium reabsorption from the urine back into the bloodstream. To maintain electrochemical balance, the reabsorption of sodium is linked with the secretion of potassium into the urine. Therefore, aldosterone effectively promotes the renal excretion of potassium, leading to lowered potassium levels in the body.

This mechanism is critical for maintaining potassium homeostasis, as elevated potassium levels can lead to serious cardiac and muscular issues. Thus, the correct answer clearly reflects aldosterone's role in increasing the renal excretion of potassium, which ultimately helps to regulate serum potassium concentration within a normal range.